Because of their versatility, electric routers are very widely used in woodworking, particularly in home and small commercial shops. Such routers are generally intended to be used by moving the router relative to a stationary work piece with a portion of the router base bearing against the work piece.
Using a router in this manner is suitable if the work piece is substantially larger than the router or is immovable. For smaller work pieces, such as the sizes used in trim work, furniture making or cabinetry, it is often more practical to invert the router such that the cutter is oriented generally upward and move the work piece. As the base of such routers is too small to be used safely in the inverted configuration, a standard practice is to affix the router to the underside of a larger table surface. In addition to addressing the safety concerns, a router table also provides the means for additional functionality as provided through accessories such as a fence, sled or miter gauge.
In order to use a router in such a configuration, it is necessary that the router be affixed to the underside of the table using non-permanent means. Most routers available on the market include a plurality of threaded holes in the base into which standard machine screws may be inserted. These screws can be used to attach the router directly to the router table or to a plate that is then attached to the table in some manner. There is no standard or common hole pattern among router bases, so a router table compatible with the greatest number of routers will require numerous extra holes in addition to those actually used to affix the router. These holes can interfere with use of the router table.
The base of many routers includes a pair of fence mounting holes whose axes are parallel to each other but normal to that of the router cutter. Although these holes can be used for mounting the router in a router table, there are shortcomings. Not all routers have such fence mounting holes. The spacing of such holes is more consistent than the base holes but still is not universal. Furthermore, because any clamping device would need to penetrate into the holes, the router cannot be quickly removed for other jobs and reattached in the same location.
Due to the versatility and control that these and other accessories provide, operations that would normally be achieved by moving the router or using a completely different woodworking tool are executed on a router table. An example is a dado. To further enhance the safety and utility provided by a router table, the overall size is increased. The design of a desirable router table must take into consideration the need to adjust the various router settings as well as access to the router to change cutters.
In designs where the router is attached directly to the table, using screws or clamps, the size of the table is limited by the need to access the router either from below or by lifting the entire table. In practice, the largest size that will enable needed access is less than that desirable for maximum safety and utility.
This problem is overcome by attaching the router to a plate that is then recessed into or attached to the peripheral table. This construction effectively solves the size problem but the separate surfaces of the plate and peripheral table introduce a discontinuity in the surface that often affects the utility of the router table. Thus the transition between these two surfaces must be selectively adjustable in order to ensure that work pieces traveling over the transition are unimpeded.
Many prior router tables achieve this adjustment by utilizing two sets of mechanical fasteners such as machine screws. The first set is used to lift the plate to the proper height, while the second set fixes the location by holding the plate down.
Other approaches use similar mechanical fasteners to increase the thickness of the plate which rests on a rim or ledge in the peripheral table surface. Other mechanical fasteners are used to hold the plate down.
A common element of these prior approaches is the inclusion of mechanical fasteners that affix the plate to the table surface at whatever height is set by other means. This, however, has the same shortcoming as attaching the router directly to the table. Prior approaches also hold the router table plate in position solely by gravity. While this allows the plate and router to be easily removed for adjustment or bit changes, it does not prevent vibration, nor can it compensate for slight distortion in the plate and or surrounding table material.
In use, a router attached to a plate in a router table can be accessed for adjustments or cutter changes by removing the router and plate assembly from the table surface, making any adjustments necessary and re-inserting the router and plate assembly.
Ideally, the transition between the plate and table surface is continuous, and the plate lacks any features that will allow a user to grip the plate in order to lift the router and plate assembly. It is thus necessary for the user to lift the router and plate from below the table surface. This operation can be difficult or impossible if the area below the table surface is used for other purposes or is closed off, such as for dust collection or storage.
It is thus desirable to provide a device that will allow a router and plate assembly to be lifted or partially lifted above a table surface from a location on the perimeter of the table surface.
Desirably, such a lifting device should be strong enough to provide the force required to lift a router and plate assembly free of whatever structure and force that secures the assembly in position for use.